The invention relates to a wiper arm, especially those used for cleaning windshields of motor vehicles.
A wiper arm is already known from DE-0 34 28 795, the fixing part of which is not manufactured by diecasting, but is formed of sheet metal. The fixing part essentially consists of one single plane plate, at which cheeks are laterally set up and which is deep-drawn to form a collar in the area of the bore for the wiper shaft, with the collar surrounding said bore. The collar tapers conically according to a conical fixing section of the wiper shaft. Although this design is satisfactory for some applications, the drafted fixing part made of sheet metal may not meet the strict strength and stability requirements of some applications.
DE-OS 39 26 714 also shows a wiper arm with a fixing part made of sheet metal. Here, the fixing part comprises an upper sheet metal section and a bottom sheet metal section integrally connected with said upper sheet metal section and parallely situated to it, the sections being supported against each other by means of side cheeks set up by the one sheet metal section, along the outline to be recognized when looking at the wiper arm in direction of the axis of the bore. In this case the one sheet metal section is seen as upper sheet metal section, which is further away from the windshield than the other sheet metal section when the wiper arm lies on a windshield. In order to increase the stability of this box-shaped fixing part in the area of the bores above all, a collar deep-drawn from the bottom sheet metal section and surrounding the bore is pressed into a hole of the upper sheet metal section. The manufacturing of such a fixing part, especially the pressing-in of the collar of the bottom sheet metal section into the hole of the upper sheet metal section is relatively difficult. By pressing-in the collar into the upper sheet metal section this collar is well supported by the upper sheet metal section in a radial direction, however, the support of the two sheet metal sections in axial direction of the bore still is lacking.
The object of the invention is to improve upon a wiper arm in such a way that the stability of the fixing part is enhanced.
This object is achieved according to the present invention by a wiper arm comprising a sheet metal section supported around the bore against a flat side of the other sheet metal section at a distance from the outline of the fixing part to be recognized, when looked at in direction of the axis of the bore. While in known fixing parts having an upper sheet metal section and a bottom sheet metal section, these two sections are axially supported against each other only via the side cheeks at the outline of the fixing part, and therefore only a bolster effect is achieved by the collar around the bore. In a wiper arm according to the invention, a full axial support is given near the bore. This is achieved in an easy way in that the one sheet metal section is supported at a flat side of the other sheet metal section.
In a preferred embodiment several integrally connected sheet metal sections of the fixing part are folded in such a way that they directly lie on each other flatly and that at least around the bore at least double thickness of material is provided. Such a fixing part can be manufactured in an especially easy manner, as deformations of material are limited.
Advantageously, a sheet metal section has the outline of the fixing part looked at in direction of the axis of the bore. The other sheet metal section can be essentially smaller in the area of the bore. In order to give the wiper arm a pleasing appearance, but also in order to avoid any edges, gaps, depressions or the like in which dirt and water can collect to occur on its surface turned away from the windshield which is to be cleaned, the upper sheet metal section preferably has the outline of the fixing part.
In order that the bore does not widen too easily in the single sheet metal layers preferably each sheet metal layer includes one single sheet metal section leading around said bore. Consequently, the edge of the bore is without a seam.
In a preferred embodiment of the wiper arm two sheet metal sections of the fixing part are folded round an edge situated behind the bore running crosswise to the longitudinal direction of the fixing part. In another preferred embodiment two sheet metal sections of the fixing part are folded around an edge of the longitudinal side. In a preferred embodiment a wiper arm is presented in which a second sheet metal section is folded around the one edge of the longitudinal side of a first sheet metal section and a third sheet metal section is folded around the opposite edge of the longitudinal side of the first sheet metal section. In this way edges of the longitudinal sides of the fixing part are provided which are rounded on both sides. The second and the third sheet metal section each preferably cover approximately half of the first sheet metal section, seen crosswise to the longitudinal direction of the fixing part. In order to avoid a seam in the bore in the sheet metal layer between the second and the third sheet metal section the second sheet metal section is widened in the area of the bore especially as far as up to the edge of the first sheet metal section. This causes the third sheet metal section to become correspondingly smaller or to completely disappear. In order to further increase the stability of the fixing part, the second sheet metal section and the third sheet metal section engage each other in the way of a dovetail at their front sides. It is possible to fold two sheet metal sections on each other, which are completely identical at least in sections. The front sides of these two sheet metal sections are visible when looking upon the fixing part vertically relative to the direction of the axis of the bore. If left uncovered, the sharp edges of the fixing part would pose a danger. The fixing part would be very sharp in the area of these uncovered front sides. Therefore, in a preferred embodiment the sheet metal section having the outline of the fixing part includes an upright standing cheek at the side of the edge, the height of which corresponds to the total thickness of the sheet metal sections lying on top of each other and which covers the front side of another sheet metal section, seen vertically to the axis of the bore.
Because a simple folding is only possible around a straight edge, a folding edge is provided between two sheet metal sections and only reaches as far as a plane, which, going through the axis of the bore, runs vertically to the longitudinal direction of the fixing part. Behind this plane the outline of the fixing part can be formed easily by an arc of a circle, the center of which is placed one the axis of the bore.
By folding the sheet metal, it is possible to obtain more than a twofold thickness of material in the area of the bore of the fixing part. For this purpose, in a preferred embodiment a second sheet metal section with an opening is folded around a first edge of the longitudinal side and a third sheet metal section with an opening is folded around a second edge of the longitudinal side of a first sheet metal section. Preferably the sheet metal sections are folded in such a way that the second sheet metal section lies on top of the first sheet metal section, and the third sheet metal section lies on top of the second sheet metal section. The first sheet metal section reaches as far as to the coupling point of a joint piece and comprises the means for coupling the joint piece at side cheeks that are bent away from said sheet metal section. In another preferred embodiment a first and a second sheet metal section with an opening are each folded with one another and the second and a third sheet metal section with one opening are folded with one another. The third sheet metal section may be situated between the first and the second sheet metal section.
In order to obtain a more than threefold thickness of material in the area of the bore a preferred embodiment is disclosed in which a second sheet metal section is folded around a first edge of the longitudinal side and a third sheet metal section is folded around a second edge of the longitudinal side of a sheet metal section. Additionally, a fourth sheet metal section with an opening is folded around an edge of the cross side of the first sheet metal section. In this case the fourth sheet metal section preferably directly bears against the first sheet metal section.
If two sheet metal sections lying on top of each other are spaced from each other, it is possible, to support the one sheet metal section by an upright standing against a flat side of the other sheet metal section. In this case this upright standing edge has a distance from the outline of the fixing part. If the sheet metal section with the upright standing edge is smaller in its outline than the other sheet metal section, the upright standing edge can be situated at the outline of the corresponding sheet metal section. A preferred embodiment is disclosed in which the upright standing edge is situated at the opening of the corresponding sheet metal section belonging to the bore.
The stability of shape of the fixing part of a wiper arm is further improved by providing sheet metal sections lying on top of each other and interconnected at various locations. A connection by spot welding or self-riveting is preferred in this case.
It is common today to place a wiper arm with its fixing part on a conically tapening, knurled fixing section of the wiper shaft. Accordingly the bore in the fixing part of the wiper arm is also conical. In a wiper arm according to the present invention the adjustment of the bore to the conically tapening fixing section of the wiper shaft is preferably achieved in such a way that the bore is provided with a constant diameter within a sheet metal section, seen in axial direction, and that the diameter increases from sheet metal section to sheet metal section by the same amount as the diameter of the conical section of the Wiper shaft, onto which the fixing part can be fitted by way of the bore. In case higher torques are to be transferred, it is favourable, to press a cone in the stepped bore with a.
A conically tapering bore may be manufactured or worked by metal cutting after the folding of the fixing part.